Construction keying

= Construction Keying =

Construction keying uses small discs, bearings or other spacers within the pin stack to allow related but dissimilar keys to open a series of locks that can later be revoked by using a different key.

Principles of operation
When new subdivisions of homes are constructed, a general contractor will provide a general key for a neighborhood to carpenters, painters, and other contractors. This allows easy access to several homes without requiring different keys, and prevents duplication and later entry into the homes once a homeowner moves in.

When the homeowner moves in, their key will be cut similar to the construction key -- which will allow the balls or wafers to enter the bible. When the plug is rotated, the spring tension will push the spacers into extra holes cut into the plug.

Vulnerabilities
Measuring the pin depth of your key, and adding the size of the spacers to the depth will allow the construction key depths to be derived. From this, permutations can be determined which may allow entry to other homes by the same builder.